Ever pick up a glass of orange juice and wonder how much your morning drink contributes to global warming? It's about time we begin questioning the everyday things in our lives to see how our lifestyles are contributing to the growing climate change problem.

According to a recent article in the New York Times, in an effort to answer increasing public concern, PepsiCo, which owns the Tropicana brand, decided to use orange juice as a case study. The company became interested in determining its product's carbon footprint in England, where carbon anxiety is more apparent than in the United States. In 2007, Walkers, a PepsiCo potato chip brand, published the carbon footprint of its product on its Website and package.The process of making orange juice seems relatively straightforward, and therefore, easy to calculate its footprint. Oranges are picked by hand, trucked to the plant, squeezed, pasteurized, packed into cartons and shipped by train to distribution points around the country. Tropicana made its own rough carbon footprint calculations before the Carbon Trust, an outside auditor, made its official calculations. It turns out that Tropicana's initial estimate was off by more than 20 percent. Why?

Fertilizer.

According to the article, growing the oranges--and producing and applying fertilizer--accounted for about a third of the carbon produced in the entire process, which is way more than PepsiCo had predicted. Citrus groves use a lot of nitrogen fertilizer, which requires natural gas to make. The fertilizer can then turn into a potent greenhouse gas when it is put onto the fields.

Similarly, Nancy Hirshberg, vice president for natural resources at the yogurt maker Stonyfield Farm, said in the article that measuring a product's carbon footprint is a good tool for companies to pinpoint areas to reduce emissions. Stonyfield Farm, like PepsiCo, was surprised to learn that production--in this case, the production of milk--was a far bigger contributor to greenhouse gas emissions than its factory.

Although putting a number on a package can be misleading and somewhat complicated to fully comprehend, figuring out a company's footprint is a great tool for companies looking to reduce their impact on climate change.

Since figuring out its carbon footprint, PepsiCo said it plans to work with its growers and researches to find ways to grow oranges using less carbon. The company is even thinking of ways to teach the public how to interpret the carbon footprint of a product. In addition to Tropicana, PepsiCo is publishing carbon footprint numbers for such products as Pepsi, Diet Pepsi and Gatorade.

Hopefully PepsiCo's work can challenge other companies to increase their transparency by publicizing the hidden costs of their products!